added coverage/ to gitignore
added coverage/ to gitignore

sbolel/firebase-util,sbolel/firebase-util,bookbottles/firebase-util,maksymilian-majer/firebase-util,dreadjr/firebase-util,googlearchive/firebase-util,maxrevilo/firebase-util,googlearchive/firebase-util,maxrevilo/firebase-util,bookbottles/firebase-util,dreadjr/firebase-util,maksymilian-majer/firebase-util